1. Field of Invention
The present invention relates to a preventive or alleviative agent for hypertension or medical symptoms caused thereby comprising as its active ingredient a dioxabicyclo3.3.0!octane derivative, a food or beverage having the effect of preventing or alleviating hypertension or medical symptoms caused thereby comprising a dioxabicyclo3.3.0!octane derivative or an extract comprising said derivative as its active ingredient, and a process for production thereof.
2. Related Art
Although the condition in which blood pressure remains continuously high is referred to as hypertension, there are considerable differences of opinion in the art with respect to what degree of high blood pressure constitutes hypertension. The World Health Organization (WHO) has made the following criteria based on epidemiological considerations. Namely, the normal range of blood pressure is set at 140/90 mmHg or less, and blood pressure of 160/95 mmHg and above is considered to constitute high blood pressure. However, in addition to a certain degree of correction required according to age and sex, in the clinical setting, there are many practitioners who consider blood pressure in excess of 150/90 mmHg to constitute high blood pressure.
Although there are various diseases that bring about hypertension, these can be broadly classified into essential hypertension, for which the cause is unknown, and secondary hypertension, for which there is a definite cause. Examples of diseases that cause secondary hypertension include kidney diseases such as glomerulonephritis and pyelonephritis, renal artery arctation, endocrine diseases such as primary aldosteronism, Cushing's syndrome (both of which are adrenocortical tumors) and melanocytoma (an adrenomedullary tumor), aortic arctation, certain types of central nervous system diseases and others. On the other hand, essential hypertension is responsible for the largest portion of hypertension cases, accounting for roughly 80% of all hypertension cases. The cause remains unknown at present, and although genetic factors have clearly been shown to be involved, details of the genetic mode are unknown.
Essential hypertension frequently occurs between the ages of 35 and 40. In the beginning, blood pressure is labile, and with the exception of the rise in blood pressure, hypertension does not exhibit any other extraordinary subjective or objective symptoms. With the passage of time, high blood pressure becomes continuous, eventually leading to left ventricular hypertrophy, arteriosclerosis and arteriolosclerosis, and causing ischemic diseases of the brain, heart and kidney. As the patient enters adulthood and old age, hypertension eventually causes death due to cerebral hemorrhage, cerebral thrombosis, congestive heart failure, myocardial infarction or uremia. Thus, hypertension is a disease that has a detrimental effect on various vascular diseases, and in particular, vascular disorders of the heart and brain. The extent to which hypertension can be prevented and treated is therefore an important issue for modern medicine.
At present, although it is possible to lower blood pressure even in the most serious cases of hypertension due to the remarkable progress that has been made in the area of depressors, conversely numerous problems remain to be solved with respect to adverse side effects of these drugs. Since treatment of hypertension requires drug therapy over an extended period of time (usually the life of the patient), there is a need for a drug that has minimal adverse side effects while offering even greater efficacy. In addition, since the particular depressor that is suitable for an individual may vary even for the same type of hypertension, various types of different depressors are necessary. Moreover, there is also a need for a mild depressor that is essentially free of adverse side effects in cases of hypertension that are not that serious.
On the basis of these viewpoints, research has recently been conducted on a plant extract to be used in pharmaceutical applications that has blood pressure lowering effects. Differing from conventional depressors such as calcium antagonists and .beta.-blockers, this plant extract preparation has hardly any adverse side effects, and is considered to occupy an important position in applications to self-medication. Particularly in the society of today with its extremely high levels of stress, there are many persons suffering from symptoms of stress, which can be considered to be a precursor of hypertension. A natural pharmaceutical preparation that is extremely safe and offers excellent efficacy is needed by these people.